trichite

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A small, dark, needle-shaped crystal.

from The Century Dictionary.

• noun A kind of flesh-spicule or microsclere of some sponges; a fibrillate spicule, in which the silica, instead of being deposited in concentric coatings around an axis, forms within the scleroblast a sheaf of exceedingly fine fibrillæ which may be straight or twisted; also, one of these fibrillæ: as, “fine fibrillæ or trichites,”
• noun In lithology, one of various dark-colored (or even black) opaque microliths, having more or less of a curved and twisted form: frequently seen in thin sections of vitreous rocks, especially in obsidian.
• Same as trichitic.
• noun One of the minute acicular crystals of which the starch-grains of plants are supposed to consist.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Min.) A kind of crystallite resembling a bunch of hairs, common in obsidian. See Illust. of Crystallite.
• noun (Zoöl.) A delicate, hairlike siliceous spicule, found in certain sponges.
• noun (Zoöl.) one of the small sheaflike fascicles of slender setæ characteristic of certain sponges. See Illust. under Spicule.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mineralogy A kind of crystallite resembling a bunch of hairs, common in obsidian.
• noun zoology A delicate, hair-like siliceous spicule, found in certain sponges.